IV THE LESSON OF THE BRITISH FLORA 



33 



in Chapter XII, are so various, that it appears at first sight im- 

 possible to connect them with the xerophilous or hygrophilous 

 organisation of a plant, or, in other words, with any structural 

 characters associated with particular stations ; yet behind all lies 

 the general principle that, given a plant of the buoyant group, 

 if it is a Xerophyte it finds its way to the coast, and if a Hygrophyte 

 it makes its home by ponds and rivers. In the case of a tropical 

 littoral flora, such as we find in a Pacific island, the large proportion 

 of plants with buoyant fruits or seeds gives so much prominence to 

 the subject of their distribution by currents that the question of 

 " station " is often masked. On the other hand, in the shore-flora 

 of a temperate region like that of Great Britain, the plants with 

 buoyant seeds or fruits are in the minority, and the question of 

 " station " is the first to obtrude itself 



In establishing the principle that most of the plants with 

 buoyant seeds or fruits have been gathered at the water-side, it 

 was never implied that all the plants by the river or by the pond 

 or at the coast are thus characterised. There is much to learn 

 from the circumstance that whilst nearly all plants with buoyant 

 seeds or fruits are placed at the water-side, not all water-side plants 

 have buoyant seeds or fruits. In the first place, it is to be inferred 

 in the light of what has been said above that the first determining 

 principle in the selection of a station is concerned not with the 

 buoyancy of the seeds or fruits, but with the xerophytic or hygro- 

 phytic organisation of a plant. In other words, it is the fitness or the 

 unfitness of a plant for living in situations where the loss of water 

 by transpiration requires to be checked that primarily determines 

 the station at the coast. We thus see in the internal organisation 

 of the plant the primary determining influence on station. Buoyancy 

 of seed or fruit comes subsequently into play, the Xerophyte and 

 the Hygrophyte, thus endowed, ultimately finding their way, the 

 first to the beach, the second to the bank of the river or to the 

 margin of the lake or pond. 



In the next place, when we regard the composition of the 

 British coast-flora, and examine the distribution of the plants 

 in other situations than on the beach, we obtain some interesting 

 results. There is first a group of plants, including such as Armeria 

 vulgaris, Artemisia maritima, Cochlearia ofificinalis, Erodium mari- 

 timum, Matricaria inodora, Plantago coronopus, Polycarpon tetra- 

 phyllum, Raphanus maritimus, Spergularia rubra, Silene maritima 

 (see Note 15), and others, all of which occur not only at the coast 

 and on the adjacent hill-slopes, but also often far inland, and 

 VOL. II D 



